How can user add multiple marker on google maps flutter

Question

How can the user add multiple markers when user long press on the map. in this code, I've done single map. when user long press on the map it will automatically add one marker but I don't know how I can add multiple markers on the map. I tried lots of codes but I am not getting the proper result. hope you understand the question. your small help can make my day. Thanks in advance.

Here is the code I've tried :)

import 'package:flutter/material.dart';
import 'package:geocoder/geocoder.dart';
import 'dart:async';

import 'package:google_maps_flutter/google_maps_flutter.dart';

void main() => runApp(MyApp());

const kGoogleApiKey = "API_KEY";

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(title: "MAP", home: BspAddressmapscreen());
  }
}

class BspAddressmapscreen extends StatefulWidget {
  BspAddressmapscreen({Key key}) : super(key: key);

  @override
  _BspAddressmapscreenState createState() => _BspAddressmapscreenState();
}

class _BspAddressmapscreenState extends State<BspAddressmapscreen> {
  final homeScaffoldKey = GlobalKey<ScaffoldState>();
  Completer<GoogleMapController> _controller = Completer();

  @override
  void initState() {
    super.initState();
  }

  double zoomVal = 5.0;

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: AppBar(
        leading: IconButton(
            icon: Icon(Icons.arrow_back_ios),
            onPressed: () {
              /*NavigationHelper.navigatetoBack(context);*/
            }),
        centerTitle: true,
        title: Text("Business Address Detail"),
        actions: <Widget>[
          IconButton(
            icon: Icon(Icons.search),
            onPressed: () {},
          ),
        ],
      ),
      bottomNavigationBar: Container(
        color: Colors.transparent,
        height: 56,
        child: Row(
          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
          children: <Widget>[
            new FlatButton.icon(
              icon: Icon(Icons.arrow_back_ios),
              label: Text('Show Address'),
              textColor: Colors.blue,
              shape: RoundedRectangleBorder(
                borderRadius: BorderRadius.circular(7),
              ),
              onPressed: () {
                getUserLocation();
              },
            ),
          ],
        ),
      ),
      body: Container(
        height: double.infinity,
        width: double.infinity,
        child: Stack(
          children: <Widget>[
            _searchbar(),
            _buildGoogleMap(context),
            _zoomminusfunction(),
            _zoomplusfunction(),
          ],
        ),
      ),
    );
  }

  getUserLocation() async {
    markers.values.forEach((value) async {
      print(value.position);
      // From coordinates
      final coordinates =
          new Coordinates(value.position.latitude, value.position.longitude);
      var addresses = await Geocoder.google(kGoogleApiKey)
          .findAddressesFromCoordinates(coordinates);

      print("Address: ${addresses.first.featureName}");
      print("Address: ${addresses.first.adminArea}");
    });
  }

  Future<void> _minus(double zoomVal) async {
    final GoogleMapController controller = await _controller.future;
    controller.animateCamera(CameraUpdate.newCameraPosition(
        CameraPosition(target: LatLng(40.712776, -74.005974), zoom: zoomVal)));
  }

  Future<void> _plus(double zoomVal) async {
    final GoogleMapController controller = await _controller.future;
    controller.animateCamera(CameraUpdate.newCameraPosition(
        CameraPosition(target: LatLng(40.712776, -74.005974), zoom: zoomVal)));
  }

  Map<MarkerId, Marker> markers = <MarkerId, Marker>{};

  Widget _buildGoogleMap(BuildContext context) {
    return Container(
      height: MediaQuery.of(context).size.height,
      width: MediaQuery.of(context).size.width,
      child: GoogleMap(
        mapType: MapType.normal,
        initialCameraPosition:
            CameraPosition(target: LatLng(40.712776, -74.005974), zoom: 12),
        onMapCreated: (GoogleMapController controller) {
          _controller.complete(controller);
        },
        markers: Set<Marker>.of(markers.values),
        onLongPress: (LatLng latLng) {
          // creating a new MARKER

          final MarkerId markerId = MarkerId('4544');
          final Marker marker = Marker(
            markerId: markerId,
            position: latLng,
          );

          setState(() {
            markers.clear();
            // adding a new marker to map
            markers[markerId] = marker;
          });
        },
      ),
    );
  }

  Widget _searchbar() {
    return Positioned(
      top: 50.0,
      right: 15.0,
      left: 15.0,
      child: Container(
        height: 50.0,
        width: double.infinity,
        decoration: BoxDecoration(
            borderRadius: BorderRadius.circular(10.0), color: Colors.white),
        child: TextField(
          decoration: InputDecoration(
            hintText: 'Enter Address',
            border: InputBorder.none,
            contentPadding: EdgeInsets.only(left: 15.0, top: 15.0),
            suffixIcon: IconButton(
              icon: Icon(Icons.search),
              //onPressed: searchandNavigate,
              onPressed: () {},
              iconSize: 30.0,
            ),
          ),
          onChanged: (val) {
            setState(() {
              // searchAddr = val;
            });
          },
        ),
      ),
    );
  }
}

Solution 1

Let's start with creating a helper function that creates a new marker and adds it to the markers map.

 onLongPress: (LatLng latLng) {
          // creating a new MARKER

          var markerIdVal = markers.length + 1;
          String mar = markerIdVal.toString();
          final MarkerId markerId = MarkerId(mar);
          final Marker marker = Marker(markerId: markerId, position: latLng);

          setState(() {
            markers[markerId] = marker;
          });
        },

Solution 2

just check below code .

main.dart

import 'package:flutter/material.dart';
import 'package:flutter_google_map/appconstant.dart';
import 'dart:async';

import 'package:google_maps_flutter/google_maps_flutter.dart';

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
  }

class _MyAppState extends State<MyApp> {

  Completer<GoogleMapController> _controller = Completer();

  Iterable markers = [];

  Iterable _markers = Iterable.generate(AppConstant.list.length, (index) {
    return Marker(
      markerId: MarkerId(AppConstant.list[index]['id']),
      position: LatLng(
        AppConstant.list[index]['lat'],
        AppConstant.list[index]['lon'],
      ),
      infoWindow: InfoWindow(title: AppConstant.list[index]["title"])
    );
  });



  @override
  void initState() {
    setState(() {
      markers = _markers;
    });
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Maps Sample App'),
          backgroundColor: Colors.green[700],
        ),
        body: GoogleMap(
          mapType: MapType.normal,
          initialCameraPosition: CameraPosition(target: LatLng(23.7985053,                          
          90.3842538), zoom: 13),
          onMapCreated: (GoogleMapController controller) {
            _controller.complete(controller);
          },
          markers: Set.from(markers),
        ),
      ),
    );
  }
}

another class for list data

appconstant.dart

class AppConstant {
  static List<Map<String, dynamic>> list = [
    {"title": "one", "id": "1", "lat": 23.7985053, "lon": 90.3842538},
    {"title": "two", "id": "2", "lat": 23.802236, "lon": 90.3700},
    {"title": "three", "id": "3", "lat": 23.8061939, "lon": 90.3771193},
  ];
}

Comments

[Lukas]

you are clearing your markers list every time the onLongPress listener is triggered. Thats why you will allways see only one - the last - set marker. Try adding new markers to the list

[Rutvik Gumasana]

Okay i've removed that marker.clear(). now can you help me what i have to do next

[Anirudh Bagri]

You are creating marker with the same marker id everytime, i.e. 4544 , this is why the same marker gets replaced everytime the screen is painted on setState

[Rutvik Gumasana]

Okay @AnirudhBagri can you please help me with that, because I've tried but not succeed. Your help can make my day :)

[Rutvik Gumasana]

i am getting error when i am using markers.add(marker) it shows the error in add method

[Rutvik Gumasana]

what will comes inside this method MyWayToGenerateId() Please help me because i am bit new in flutter

[Rutvik Gumasana]

The method 'add' isn't defined for the class 'Map'. Try correcting the name to the name of an existing method, or defining a method named 'add'

[Anirudh Bagri]

try using markers[markerId] = marker. Maps don't have add method

[Rutvik Gumasana]

should i need to add return markers.length + 1 in set state ???

[Anirudh Bagri]

Edited my answer and removed the method of creating new id. this should help.

[Lukas]

This should work. It is exactly the same like your accepted answer. I only use a counter var which obviously has to be initiated

[Rutvik Gumasana]

Hey bro i've little bit edited your answer and it's working fine :) Thank you so much for your help :)

[Rutvik Gumasana]

no it's not working. but thank you so much for your help :)

[Rutvik Gumasana]

if you feel that this question is useful then please upvote it. because of there no question similar like this on the stack overflow

[Rutvik Gumasana]

if you feel that this question is useful then please upvote it. because of there no question similar like this on the stack overflow

[Rutvik Gumasana]

can you please tell me how can i remove added markes